Denture and method and apparatus of making same

ABSTRACT

A method for making a denture comprising a base and a plurality of teeth joined thereto. The method comprises forming a first cavity in a block of a denture base material, the first cavity being formed to match the contour of natural teeth as arranged on maxillae or on a mandible; filling the first cavity with a first fluid synthetic tooth material and solidifying the first fluid synthetic tooth material into a first solid synthetic tooth material; removing a portion of the first solid synthetic tooth material to form the plurality of teeth; and removing a portion of the block of denture base material to form the denture base. The steps of the method may be implemented by a computer. An apparatus for making the denture according to certain embodiments of the method, and a denture comprised of a base and artificial teeth are also disclosed.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication No. 61/539,970, filed Sep. 27, 2011, the disclosure of whichis incorporated herein by reference.

BACKGROUND

1. Technical Field

Dental prostheses and apparatus and methods of manufacturing them. Inparticular, computer-implemented methods of manufacturing dentalprostheses, a computer-aided system for manufacturing dental prostheses,and dental prostheses made by the system and method.

2. Description of Related Art

Heretofore, the manufacturing of dental prostheses has been a highlylabor intensive process requiring multiple fittings to a patient in needof them, and many steps that must be performed at the hands of skilledartisans. The dental prostheses may be a complete upper and/or lower setof prosthetic teeth and their mountings, i.e., dentures, or partialdentures, crowns, bridges, and the like.

By way of illustration, the following are the steps currently practicedin many “dental laboratories” for the fabrication of a conventionalfixed dental prosthetic known as a crown:

-   -   1) A dentist prepares the tooth (or teeth) to be fitted with a        fixed prosthetic by removing tooth structure that is decayed or        to allow for space needed by the prosthetic device.    -   2) An accurate impression of the patient's existing gums and        prepared teeth is made by the dentist at the dentist's office.    -   3) Gypsum material is poured into the impression to form a model        (replica) of the dentition to be treated.    -   4) Wax is typically used to make a coping (thin metal        substructure) on the model.    -   5) Using the “lost wax technique”, the wax is invested (covered)        by a phosphate investment material and then it is heated to        burn-out (remove) the wax, leaving a void in its place.    -   6) Metal is cast into the void created by the loss of wax to        create a metal coping.    -   7) The metal coping is finished with grinding stones and        typically heat-treated.    -   8) Porcelain powder dispersed in water is painted onto the metal        coping.    -   9) The porcelain is fired in a furnace to sinter it into a        continuous hard coating, resulting in the finished crown.

It can be seen that in the above highly labor-intensive process, each ofthese steps introduces a potential for a processing error. Even theslightest error, such as the investment being too cool, or thepowder/water ratio of the investment being incorrect may cause the crownto fit too tightly in the patient's mouth, resulting in improperocclusion (upper and lower teeth engagement). The crown may thus have tobe scrapped or reworked through at least one iteration of additionalprocess steps at considerable cost to the patient, dentist, and/ormanufacturing lab.

Currently, Computer Aided Design and Computer Aided manufacturing(CAD/CAM) for “fixed” restorative dentistry has evolved to the pointwhere a digital impression can now be made in the dentist's office andthe entire process can be computer implemented. However, certainshortcomings still remain in fixed restorative dentistry as presentlypracticed. For example, subtle irregularities often found in anterior(front) teeth are difficult to replicate using CAD/CAM processes. Manualmethods of making anterior fixed prosthetics enable unlimited aestheticoptions, only limited by the creativity of the artisan (dentallaboratory technician). Some CAD/CAM techniques involve the use ofmilling a monolithic block of ceramic that does not deliver optimalaesthetics (example: too opaque), especially for anterior applications.For example, most natural teeth exhibit translucency and subtle colorvariations. A common solution for this problem is for a dentaltechnician to apply a stain and/or glaze of porcelain over theprosthetic made by CAD/CAM. However, this manual step may defeat theprimary benefit of CAD/CAM: precise dimensional accuracy.

With regard to the manufacturing of removable dental prosthetics, suchas dentures and partials, implementation of CAD/CAM has begun to occur.A key technology that is used in CAD/CAM denture manufacturing is “fuseddeposition modeling” (FDM). In FDM, a computer-controlled machine buildsa three dimensional part by ejecting microscopic droplets of materialwhile repeatedly traversing in an x-y plane, building the part layer-bylayer. In a sense, the machine “ink-jet prints” each layer, and henceFDM is also referred to as “3D printing.” The physical model is builtaccording to a three-dimensional virtual model that is prepared usingCAD software and uploaded to the FDM machine.

CAD/CAM systems have recently been developed and used for thefabrication of partial denture frameworks. One such system uses a“haptic” device, which mimics a waxing tool that is familiar to dentaltechnicians. However, this system generates only a CAD replica inplastic (made by a 3D printer), which requires subsequent extensiveprocessing to obtain a metal partial denture framework. Hence there arestill many error-prone steps after the CAD replica is made that canresult in a poorly-fitting partial denture framework.

There have been some efforts by major manufacturers of dental materialsto make a system to produce a complete (full) denture by 3D printing.The system includes a 3-dimensional scanner for scanning an impression,software for creating a 3-dimensional model of the denture, and thefused deposition modeling equipment for “printing” the denture. However,the materials available to use in 3-dimensional printers are neither asdense nor cross-linked like a normal plastic artificial tooth. Hence aproblem remains with the resulting dentures because the denture teeththat are made with available 3D printing plastic materials are notsufficiently wear-resistant.

An alternative approach to denture fabrication is to first make adenture base using a milling machine, which may be computer controlled.Sockets are then milled by the machine into the denture base, andpre-fabricated artificial teeth are placed into the sockets. A problemwith this approach is that most of the teeth must be adjusted to someextent to fit within the space required in order for the denture toproperly occlude with the opposing arch of the opposing denture or thepatients existing opposing teeth. Manual labor is required for theadjustment of teeth; therefore, the potential for errors is introducedinto the manufacturing process.

Another problem with this method is that artificial teeth are notconsistently sized. They are made from a molding process, with the moldsbeing used for many years. Over the course of use, material from thewall of the mold will wear away, resulting in a mold cavity increasingin size. Hence a tooth made from a mold that has been in service for tenyears will be larger than a tooth made when the mold was new.Additionally, molds contain multiple cavities, and the wear is notnecessarily uniform. Thus the combination of wear with time andnon-uniform wear results in the production of teeth that varydimensionally within any given tooth size. Moreover, in the denturefabrication marketplace, artificial teeth are returnable for credit. Ittherefore becomes highly probable that artificial teeth produced 20years ago from a new mold are in circulation with teeth produced veryrecently from the same but aged mold having different dimensions.

There is thus a problem in that the dimensional variation of artificialteeth is significant with respect to the dimensions of the socketsformed by the milling machine in which the teeth are to be fitted. Thesockets must be milled sufficiently large so as to receive the largesttooth encountered within a given tooth size and shape (i.e. incisor,canine, molar, etc.), and countermeasures taken when the tooth is toosmall and does not fight tightly into its socket. One countermeasure isto use an acrylic repair resin to secure the teeth into position and tofill the gap(s), of various sizes that may be present around anundersized tooth.

However, this practice is undesirable. Additional labor is required forthis step, which is costly and which is likely a manual process whichcan introduce potential errors to the denture fabrication. The risk ofdenture tooth “pop-outs” (debonding from the denture base) is morelikely because the volume of bonding material is quite small relative tothe conventional method of bonding denture teeth, and the bondingsurface may be restricted to the circumference of the denture toothwhich interfaces with the denture base (and limited bonding of the areaof the tooth that opposes the occlusal surface because this area hasbeen adjusted to rest on the “floor” of the socket). In the conventionalapproach, uncured denture base material surrounds the neck of the teethand the area of the teeth that oppose the occlusal surface and chemicalbonds are formed due to the volume of material and time that the uncuredmaterial is allowed to form cross-linked chemical bonds with theartificial teeth.

In addition, like the conventional approach, the patient will not seethe final configuration of the denture until the delivery appointment,at which time the patient may reject the denture based on esthetics.

A further reason that “pop-outs” will be more likely with this approachvs. the conventional approach is that the conventional approach relieson a dental technician to adjust each artificial tooth in a way tooptimize retention. For example, a dental technician will remove the“glaze” from a denture tooth (shiny and hard surface of the toothcreated from a metal mold) to form a better bond with the denture base.Also, “diatoric” holes are often cut into the bottom or side of thetooth, or both, to allow acrylic material to flow in an optimal path toincrease the surface area and create mechanical retention in a tooth.The step to provide diatoric holes is yet another processing step thatincreases cost and introduces the potential for further errors, such asartificial tooth fracture.

Yet another approach to denture fabrication is to mill blocks ofpolymerized plastic to make a complete denture. This process involvesmilling a block of pink methacrylate material as the denture base(including the gingiva surrounding the teeth). The teeth are then milledfrom a single piece of plastic. Lastly, the pink denture base and themilled teeth are cemented together. This technique is useful to make animmediate denture for temporary use, such as after a tooth-extractionfor use while the gums heal. However, it is not suitable for long-termdentures because the artificial teeth made in this manner lookunaesthetic. Natural dentition has subtle color (hue) variations as wellas translucencies, color volume and defects. These effects arebuilt-into most artificial teeth which are generally made in 2 to 4layers of overlapping material (plastic or porcelain), each layer havingdifferent shades and levels of translucency. These layers create anatural effect of tooth structure, especially in anterior (front) teethwhich often display “mamelons” and translucent incisal edges.

Artificial teeth that have an aesthetically pleasing appearance aregenerally made of highly cross-linked polymethylmethacrylate plastic,but may also be made of porcelain. Such artificial teeth are made with aseries of metal dies in which the teeth are formed one-layer at a time.When all of the layers are completed, the “green” tooth is then heatedto polymerize the plastic (or super-heated in the case of porcelainteeth). The heating process completes the cross-linking process inplastic teeth to make the teeth resistant to wear from the forces ofmastication. This process is not compatible with the above overalldenture fabrication process in which the full set of teeth are milledfrom a single piece of plastic and bonded to the milled denture base.

In summary, there remains a need for a method and apparatus forfabricating a denture at low cost in a minimal number of steps and withminimal manual labor, and preferably at a single manufacturing station.A denture made by any such method and apparatus must be made withsufficient precision so as to fit the patient properly, and have teeththat are firmly retained, wear resistant, and aesthetically pleasing.

SUMMARY

In accordance with the present disclosure, the problem of fabricating adenture at low cost in a minimal number of steps and with minimal manuallabor is solved by using a block of denture base material as areceptacle for molding the teeth. The block of denture base material ismilled by a milling machine or other material removal device to create amold for the teeth. Fluid tooth material is dispensed into the mold andcured into solid tooth material. The combination of cured solid toothmaterial in the mold and denture base material are milled to form thedenture. More specifically, in certain embodiments, the problem ofmaking a denture comprised of a base and a plurality of teeth joined tothe base is solved by forming a first cavity in a block of a denturebase material, the first cavity formed to match the contour of naturalteeth as arranged on maxillae or on a mandible; filling the first cavitywith a first fluid synthetic tooth material and solidifying the firstfluid synthetic tooth material into a first solid synthetic toothmaterial; removing a portion of the first solid synthetic tooth materialto form the plurality of teeth; and removing a portion of the block ofdenture base material to form the denture base. The steps of the methodmay be implemented by a computer.

The method may further comprise heat treating the denture base andplurality of teeth. Solidifying (polymerization in certain embodiments)the first fluid synthetic tooth material may be performed by heatingand/or irradiating the first fluid synthetic tooth material. The heatingmay be provided by an exothermic chemical reaction in the fluidsynthetic tooth material (i.e., self heating), or by an external heatsource. In instances where it is desired to make a temporary denture fortrial fitting purposes, the first solid synthetic tooth material may bea wax.

The denture may be defined by a digital three-dimensional model. In suchan embodiment, forming the first cavity may be performed based upon datafrom the three-dimensional model. Additionally, the removing a portionof the first solid synthetic tooth material to form the plurality ofteeth and the removing a portion of the block of denture base materialto form the denture base may be performed to produce the denture havingthe dimensions defined in the three-dimensional model.

In certain embodiments, the plurality of teeth may be formed by moldingtwo or more fluid synthetic tooth materials. In such embodiments, thedenture fabrication method comprises forming a first cavity in a blockof a denture base material as recited above; filling the first cavitywith a first fluid synthetic tooth material and solidifying the firstfluid synthetic tooth material into a first solid synthetic toothmaterial; forming a second cavity by removing a portion of the firstsolid synthetic tooth material, the second cavity being formed to matchthe contour of natural teeth as arranged for the contour of the firstcavity; filling the second cavity with a second fluid synthetic toothmaterial and solidifying the second fluid synthetic tooth material intoa second solid synthetic tooth material; removing a portion of thesecond solid synthetic tooth material to form the plurality of teeth;and removing a portion of the block of denture base material to form thedenture base.

The denture base and plurality of teeth may be heat treated afterformation in order to fully cross-link the polymers of the base andteeth. Solidifying the second fluid synthetic tooth material may beperformed by external heating, self-heating and/or irradiating thesecond fluid synthetic tooth material. As recited above, the denture maybe defined by a digital three-dimensional model, in which case, formingthe first cavity and forming the second cavity may be performed basedupon data from the three-dimensional model. Additionally, removing aportion of the second solid synthetic tooth material to form theplurality of teeth and the removing a portion of the block of denturebase material to form the denture base may be performed to produce thedenture having the dimensions defined in the three-dimensional model.

The method may be further comprised of filling the second cavity with athird fluid synthetic tooth material, causing the third fluid synthetictooth material to solidify into a third solid synthetic tooth material,and removing a portion of the third solid synthetic tooth material tore-form the second cavity, prior to filling the second cavity with thesecond fluid synthetic tooth material.

The second solid synthetic tooth material may differ from the firstsolid synthetic tooth material. In certain embodiments, the second solidsynthetic tooth material may be synthetic translucent tooth enamelmaterial.

The method may be used to make a trial denture in which the first solidsynthetic tooth material is a wax. The trial denture may then be fittedto a patient, and final adjustments made to the positions of therelatively soft wax synthetic teeth and/or base. The fitted trialdenture may then be scanned in three dimensions to obtain scanneddenture data, which may then be used to produce the digitalthree-dimensional model. The 3D model may then be used by a computer tocontrol the denture-making apparatus to produce the final denture asdescribed herein.

The method may be used to make a trial denture in which the denture baseis made from a suit able material such as methacrylate polymer,typically of a pink flesh-tone color. Sockets are formed in the denturebase by a milling machine, which are then filled by pink-colored wax.Then a portion of the wax and denture base is removed by the millingmachine in order to create a void that can be filled by fluid synthetictooth material made from tooth-colored methacrylate. The sockets madefrom wax are preferred because they enable a dentist to adjust theposition of the teeth if necessary in order to optimize occlusion oresthetics. Dentists are accustomed to making adjustments to trialdentures, so this method is consistent with present practice. Inaddition, the teeth can be made from multiple layers of tooth-coloredmethacrylate or other suitable polymer so that the trial denture willlook exactly like the finished denture, thereby increasing thelikelihood of patient acceptance at the final delivery appointment.

Also according to the present disclosure, an apparatus for making adenture comprised of a base and a plurality of teeth joined to the baseis provided. The apparatus is comprised of a material holding fixture, amaterial removal device, and a first fluid synthetic tooth materialdelivery device. The material removal device is contactable with a blockof denture base material held by the fixture so as to remove denturebase material and form a first mold cavity in the block for receivingthe first fluid synthetic tooth material. The first mold cavity isformed to match the contour of natural teeth as arranged on maxillae oron a mandible. The first fluid synthetic tooth material delivery deviceis configured to deliver the first fluid synthetic tooth material intothe first mold cavity.

The apparatus may be further comprised of a fluid-to-solid toothmaterial curing device configured to cure the first fluid synthetictooth material in the first mold cavity into first solid tooth material.The material holding fixture and material removal device are movablewith respect to each other so as to enable the material removal deviceto remove denture base material from the block and first solid toothmaterial in the first mold cavity so as to form the denture base and atleast a portion of the plurality of teeth.

The apparatus may be further comprised of a second fluid synthetic toothmaterial delivery device configured to deliver the second fluidsynthetic tooth material into a second mold cavity formed by thematerial removal device removing a portion of the first solid toothmaterial. In such an embodiment, a fluid-to-solid tooth material curingdevice may be configured to cure the second fluid synthetic toothmaterial in the second mold cavity into second solid tooth material.Additionally, the material holding fixture and material removal devicemay be movable with respect to each other so as to enable the materialremoval device to remove second solid tooth material in the second moldcavity so as to form at least a portion of the plurality of teeth.

The apparatus may be further comprised of a third fluid synthetic toothmaterial delivery device configured to deliver the third fluid synthetictooth material into a third mold cavity formed by the material removaldevice removing a portion of the first solid tooth material. In such anembodiment, a fluid-to-solid tooth material curing device may beconfigured to cure the third fluid synthetic tooth material in the thirdmold cavity into third solid tooth material. Additionally, the materialholding fixture and material removal device may be movable with respectto each other so as to enable the material removal device to removethird solid tooth material in the third mold cavity so as to form atleast a portion of the plurality of teeth.

Also according to the present disclosure, a denture comprised of a baseand a plurality of teeth joined to the base is provided. The teeth arecomprised of a posterior region of a first solid synthetic toothmaterial and an anterior region of a second solid synthetic toothmaterial. The second solid synthetic tooth material preferably has theappearance to an observer of natural teeth. The teeth may be furthercomprised of a third solid synthetic tooth material in an interiorregion between the first solid synthetic tooth material and the secondsolid synthetic tooth material.

As a result of the invention, certain benefits in the manufacturing ofdentures are realized. The requirement for skilled manual labor infabrication is virtually eliminated. The opportunity to use computercontrol over all steps of fabrication also eliminates many errors, aswell as making the process highly versatile. Via the use of software, adental professional may create any shape and color of teeth to match theclinical and aesthetic needs of the patient, and the method andapparatus can be employed to make them to order. In addition, a dentistcan show the patient a digital photo of his/her face with his/her newdentures, before the start of the fabrication process, therebyincreasing the likelihood of patient acceptance of the denture at thedelivery appointment. The manual expertise formerly required for toothset-up in the denture is no longer needed, because such set-up can bepredetermined using CAD software, and a digital three dimensional modelof the denture uploaded to the computer-controlled fabricationapparatus.

Additionally, the need for a dental lab to maintain a large stock ofdenture teeth is also eliminated. This is a significant cost savings, inthat some dental labs maintain over $100,000 worth of teeth in theirinventory in order to be able to timely satisfy incoming orders. Inaddition, handling costs of a large tooth inventory can be eliminated:shipping costs, ordering and stocking/retrieving costs, risk oftheft/damage, cost of handling returns of partially used sets of teeth,etc. Furthermore, the shades, shapes, anatomy, imperfections,translucency, etc. of the teeth can be custom-made for each denture.

If it is desirable to fabricate a temporary “try-in” denture with waxteeth for a test fit before fabricating a long-term denture, the methodand apparatus can be used to fabricate the try-in denture as describedpreviously, but using a wax material for the teeth. A methacrylate orother suitable denture base material is milled to form a cavity wherebytooth-colored wax is placed in the cavity to form wax teeth. Because thesynthetic teeth material is wax, in the dental office, a dentist can fitthe try-in denture to the patient, and make final adjustments tooptimize its fit and aesthetics. Then the final-adjusted try-in denturecan be scanned in 3D and digitally compared to the original “wax try-indenture” and/or used as the source of a new three-dimensional denturemodel to be used in manufacturing the long term denture. In that manner,the final denture will have optimal fit to the patient, with only onefitting session needed with him/her before the final denture isdelivered and fitted.

If it is desirable to fabricate a temporary “try-in” denture with resinteeth for a test fit before fabricating a long-term denture, the methodand apparatus can be used to fabricate the try-in denture as describedpreviously. A methacrylate denture base material is milled to formsockets where the teeth will be fabricated. The sockets are subsequentlyfilled with moldable wax. Then the apparatus mills a cavity wherebytooth-colored resin is placed in the cavity to form the teeth. Becausethe synthetic teeth material is resin in a socket made of wax, in thedental office, a dentist can fit the try-in denture to the patient, andmake final adjustments to optimize its fit and aesthetics. Additionally,the patient can see the color and translucency of the final dentureteeth before the final denture is made, thereby increasing thelikelihood of patient acceptance at the final appointment. Then thefinal-adjusted try-in denture can be scanned in 3D and digitallycompared to the original “wax try-in denture” and/or used as the sourceof a new three-dimensional denture model to be used in manufacturing thelong term denture. In that manner, the final denture will have optimalfit to the patient, with only one fitting session needed with him/herbefore the final denture is delivered and fitted.

It is also noted that in manufacturing a denture according to theinstant method, the artificial teeth are chemically bonded to thedenture base on all surfaces which the artificial teeth interface withthe denture base. This significantly reduces the likelihood of theartificial teeth detaching from the denture base (referred as a“pop-out”), and the formation of dark demarcation lines around thejunction of the artificial teeth and artificial gingiva due to bacterialgrowth. (The latter problem is often found in dentures made withporcelain artificial teeth because there is no chemical bond between thedenture base and the teeth.) Accordingly, the artificial teeth will lookmore natural.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will be provided with reference to the followingdrawings, in which like numerals refer to like elements, and in which:

FIG. 1A is a perspective view of a block of denture base material havinga first cavity being formed therein according to the method andapparatus of the present disclosure;

FIG. 1B is a cross-sectional view of the block and apparatus of FIG. 1A,taken along line 1B-1B of FIG. 1A;

FIG. 2A is perspective view of a fluid dispensing device deliveringfirst fluid synthetic tooth material into the cavity formed in the stepdepicted in FIG. 1A;

FIG. 2B is a cross-sectional view of the block of FIG. 2A, taken alongline 2B-2B of FIG. 2A, showing means for solidifying the first fluidsynthetic tooth material in the cavity in the block of denture basematerial;

FIG. 3 is a cross-sectional view of the block of denture base materialand first solid tooth material as depicted in FIG. 2B, but showing amaterial removal device removing a portion of the first solid toothmaterial to form a second cavity in the block;

FIG. 4A is perspective view of a fluid dispensing device deliveringsecond fluid synthetic tooth material into the cavity formed in the stepdepicted in FIG. 3;

FIG. 4B is a cross-sectional view of the block of FIG. 4A, taken alongline 4B-4B of FIG. 4A, showing means for solidifying the second fluidsynthetic tooth material in the second cavity in the block;

FIG. 5 is a cross-sectional view of the block of denture base materialand first and second solid tooth material as depicted in FIG. 4B, butshowing a material removal device having removed a portion of the secondsolid tooth material to form a third cavity in the block;

FIG. 6 is a cross-sectional view of the block after the dispensing of athird fluid synthetic tooth material into the cavity formed in FIG. 5,showing means for solidifying the third fluid synthetic tooth materialin the cavity;

FIG. 7 is a cross-sectional view of the block and first, second, andthird solid synthetic tooth materials, showing the beginning of thefinal material removal step to form the finished denture;

FIG. 8A is a perspective view of a finished denture made according tothe method and apparatus of the present disclosure; and

FIG. 8B is cross-sectional view of the denture of FIG. 8A, taken alongthe line 8B-8B of FIG. 8A.

The present invention will be described in connection with certainpreferred embodiments. However, it is to be understood that there is nointent to limit the invention to the embodiments described. On thecontrary, the intent is to cover all alternatives, modifications, andequivalents as may be included within the spirit and scope of theinvention as defined by the appended claims.

DETAILED DESCRIPTION

For a general understanding of the present invention, reference is madeto the drawings. In the drawings, like reference numerals have been usedthroughout to designate identical elements.

In accordance with the present disclosure, there are provided a methodand an apparatus for making a dental prosthesis, such as a denture, byusing a block of denture base material as a receptacle for molding theteeth of the denture. The block of denture base material is milled by amilling machine or other material removal device to create a mold forthe teeth, dispensing liquid tooth material in the mold and curing itinto solid tooth material, and milling the combination of cured solidtooth material in the mold and denture base material to form thedenture.

Turning first to FIGS. 1A and 1B, a block 10 of denture base material isshown in the process of having a first cavity 12 being formed therein.The first cavity 12 is formed to match the generally U-shaped contour ofnatural teeth as arranged on maxillae or on a mandible, for reasons thatwill become apparent subsequently.

The first cavity may be formed by using a mill, a portion of which isindicated by numeral 100, comprising a milling bit 102 having sideand/or end cutting teeth 104. The overall fabrication apparatus includesa combination of rotation and translation means for the block ofmaterial and for the milling bit 102 so that they are movable withrespect to each other along and around multiple axes, as is known in themachining arts. For example, the block 10 may be linearly movable alongorthogonal axes 2 and 3 and along a third axis orthogonal to axes 2 and3, and rotatable around those axes as indicated by arcuate arrows 4 and5. The milling bit 102 may be linearly movable along orthogonal axes101, 103, and 105, and rotatable around these axes. Thus the block 10and milling bit 104 are movable with respect to each other over a fullrange of motion so as to enable the milling of the intricate shapes ofcavities therein, and also the intricate shapes of the denture base andartificial teeth as will be described subsequently. It is noted that forthe sake of simplicity of illustration, the movable fixturing for theblock 10 of denture base material and the motion control devices for themilling bit 102 are not shown.

The mill 100 is preferably controlled by a computer, i.e. the mill 100is a CNC (computer numerically controlled) mill. The mill 100 mayinclude a turret and tool changer (not shown), so that multiple toolbits 102 may be used in milling the cavities in the block 10 and thefinal denture base and artificial teeth of the denture. Larger tool bitsmay be used for fast removal of large portions of material, and smallertool bits may be used for the finishing of intricate shapes of thecavities, final denture base and artificial teeth. As an example, themilling machine including the movable block fixture may be a Model DWXmill manufactured by the Roland DGA Corporation of Irvine, Calif.

It is not required that the removal material device be a millingmachine. Other material removal devices/processes are contemplated, suchas laser ablation, water jet machining, and the like.

When the forming of the first cavity 12 in the block 10 of denture basematerial is complete, the cavity 12 is filled with a first fluidsynthetic tooth material by a fluid material delivery device. In certainembodiments, as shown in FIG. 2A, the material delivery device 120 maybe a syringe 122 that contains first fluid synthetic tooth material 20.The syringe 122 may be part of a syringe pump (not shown), which mayinclude means (not shown) for controlling the displacement of thesyringe plunger 124, and means (not shown) for moving the syringe 122relative to the block 10 along orthogonal axes 121 and 123, and a thirdaxis orthogonal to them. In that manner, the syringe 122 may betraversed along the U-shape of the cavity 12 as it dispenses first fluidsynthetic tooth material therein.

Other means for delivering the fluid synthetic tooth material may besuitable, such as positive displacement metering pumps (not shown),which may include on/off valving and other delivery control devices (notshown). In other embodiments, the fluid synthetic tooth material can bedelivered under pressure into the void in the denture base wherein thedenture base is encapsulated within a flask or vacuum chamber on otherrestraining device that will enable complete filling of all voidscreated in the denture base. In certain embodiments, the means fordelivering the fluid synthetic tooth material to the cavity may be anapparatus that delivers fluid materials as performed in fused depositionmodeling, also known as “3D printing” as described previously herein.

Referring back to FIG. 1A, in addition to milling the U-shaped cavitycorresponding to the shape of natural teeth, one or more troughs (knownin the art as “sprues”) may be milled in the top surface of the block 10of denture base material. The sprues 14 and 16 extend from the cavity 12to the side wall 11 of the block 10. Alternatively, sprues (not shown)may be drilled through the side wall 11 slightly below the top surfaceof the block to the cavity 12.

In such configurations, after the forming of the cavity 12 and sprues 14and 16 or sub-surface sprues (not shown), the block 10 may be placed ina container (known in the art as a “flask”), and the fluid synthetictooth material 20 may be injected into the cavity 12 through the spruesin a manner analogous to injection molding. As noted above, vacuum maybe used to facilitate flow into or through the cavity 12.

Referring now to FIG. 2B, after the cavity 12 has received first fluidsynthetic tooth material 20, such fluid material is solidified intofirst solid synthetic tooth material 21. (It is noted that “syntheticsolid tooth material” as recited herein is meant to indicate a toothmaterial other than solid tooth material that is produced by the naturalbiological process of tooth formation.) The solidification process maybe the result of the formulation of the first fluid synthetic toothmaterial, which may be a “self-curing” material such as methylmethacrylate resin.

In certain embodiments, the solidification (or “curing”) of the firstfluid synthetic tooth material 20 may be partially or wholly caused bythe application of heat, such as by an infrared heater 130 and/or aconvection heater (not shown). In other embodiments, the solidificationof the first fluid synthetic tooth material 20 may be partially orwholly caused by irradiating the first fluid synthetic tooth material 20with a light 140. In such embodiments, the first fluid synthetic toothmaterial 20 may be formulated as a light sensitive material which may becured by the application of high-energy radiation, such as ultravioletlight. Alternatively, the light may be visible light, or the light maybe infrared light which provides heating of the fluid synthetic toothmaterial 20.

In certain embodiments, a portion of the first solid synthetic toothmaterial 21 may then be removed to form the plurality of teeth, and aportion of the block 10 of denture base material may be removed to formthe denture base, thus forming the overall finished denture 60 (FIGS. 8Aand 8B). Referring to FIG. 7, the milling bit 102 is traversed overand/or around the block 10, optionally with both the block 10 and thebit 102 moved relative to each other. Denture base material 13 isremoved from the upper region 15, the lower region 17, and the lateralregion 19 of the block 10, leaving behind the denture base 62. Tofacilitate material removal, the fixturing for the block 10 may beprovided with means (not shown) for inverting the block 10 relative tothe mill bit 102.

Additionally, the first solid synthetic tooth material 21 is removed bythe milling bit 102 as required to form the plurality of teeth 64. It isnoted that in FIG. 8B, the synthetic teeth 64 shown in cross-section areshown as comprising first solid synthetic tooth material 22, secondsolid synthetic tooth material 32, and third solid synthetic toothmaterial 42. The fabrication of teeth 64 may include a second solidsynthetic tooth material 32, and further include a third solid synthetictooth material 42 as will be explained subsequently herein.

However, the finished denture 60 may have the plurality of teeth 64 madeof only the first solid synthetic tooth material 22, but occupying theentire tooth volume/shape of the teeth 64 formed by tooth materials 22,32, and 42 in FIG. 8B. One circumstance where it may be desirable tomake a denture 60 having teeth 64 of only a first solid synthetic toothmaterial 22 is when a denture 60 is needed that is of minimal cost.Another circumstance is where it is desirable to make a temporary“try-in” denture for a test fit before fabricating a long-term denture.A solid but formable wax material may be used as the teeth 64 formedtherein. Because the first synthetic tooth material 22 are made of waxin such circumstance, in the dental office, a dentist can fit the try-indenture to the patient, and make final adjustments to optimize its fitand aesthetics. Then the final-adjusted try-in denture can be scanned inthree dimensions and digitally compared to the original “wax try-indenture” and/or used as the source of a new three-dimensional denturemodel to be used in manufacturing the long term denture. In that manner,the final denture will have optimal fit to the patient, with only onefitting session needed with him/her before the final denture isdelivered and fitted.

In certain preferred embodiments, the teeth 64 of the finished denturemay include second solid synthetic tooth material 32, and third solidsynthetic tooth material 42. Referring to FIG. 8B, the second solidtooth material 32 may be a tooth colored material with a white orslightly off-white coloration. The third solid synthetic tooth material42, which may entirely cover the second solid synthetic tooth material32 and extend upwardly past such material 32, may be a translucentmaterial. By so choosing such second and third solid synthetic toothmaterials 32 and 42, the appearance of natural teeth is best replicatedin the finished denture 60. It is also noted that in such aconfiguration, the appearance of the first solid synthetic toothmaterial 22 being “natural” is less important, because the first solidsynthetic tooth material 22 is located on the posterior region of theteeth 64, i.e., on the inside of the teeth 64 proximate to the tongue,and is thus generally not visible to others, except a dentist or otherclinician performing dental tasks or examinations.

The fabrication of the denture 60 comprising second synthetic toothmaterial 32 and third solid synthetic tooth material 42 will now bedescribed. Referring again to FIG. 3, after the first fluid synthetictooth material 20 has been cured into first solid synthetic toothmaterial 21 (FIG. 2), a second cavity 23 is formed by removing a portionof the first solid synthetic tooth material 21. The second cavity 23 isformed to match the contour of natural teeth as was done for the contourof the first cavity 12 (FIG. 1A). It is noted that in FIG. 2B and FIG.3, the filling of the cavity 12 with first liquid synthetic toothmaterial 20 is shown as completely filling the cavity 12 to the topsurface 18 of the block 10 prior to its curing into first solidsynthetic tooth material 21. However, it is not necessary to fill thecavity 12 completely; instead, the cavity 12 needs to only be filled tothe highest point of the first solid tooth material 22 that is going toremain as part of the synthetic teeth 64. The same principle applieswith respect to the filling of cavities that receive second fluidsynthetic tooth material 30 (FIG. 4A) and third fluid synthetic toothmaterial (not shown).

Referring to FIG. 4A, the second cavity 23 receives a second fluidsynthetic tooth material 30, from a suitable source such as e.g.,syringe 220. Referring to FIG. 4B, the second fluid synthetic toothmaterial 30 is solidified into a second solid synthetic tooth material31. The second fluid synthetic tooth material 30 may be solidified bythe use of a heater 130, or a light 140, or material 30 may beself-curing, all as described previously with respect to first fluidsynthetic tooth material 20.

In certain embodiments, a portion of the second solid synthetic toothmaterial 31 may then be removed to form the plurality of teeth 64, and aportion of the block 10 of denture base material may be removed to formthe denture base, thus forming the overall finished denture 60 of FIGS.8A and 8B as described previously. In such embodiments, the teeth 64 aremade of first solid synthetic tooth material 22 forming a posteriorregion of the teeth 64, and second solid synthetic tooth material 32forming the anterior region of the teeth 64. The second solid synthetictooth material 32 may occupy the additional volume occupied by thirdsolid synthetic tooth material 42 shown in FIG. 8B.

However, for reasons described previously directed to having the mostnatural appearing and aesthetically pleasing teeth 64, it is preferredto fabricate such teeth 64 to be comprised of the third solid synthetictooth material 42. This is best understood with reference to FIGS. 5-7.Referring first to FIG. 5, after the second fluid synthetic toothmaterial 30 has been cured into second solid synthetic tooth material 31(FIG. 4B), a third cavity 33 is formed by removing a portion of thesecond solid synthetic tooth material 31. The second cavity 33 is formedto match the contour of natural teeth as was done for the contours ofthe first and second cavities 12 and 23 (FIG. 1A and FIG. 3).

The third cavity 33 receives a third fluid synthetic tooth material froma suitable source such as a syringe (not shown). Referring to FIG. 6,the third fluid synthetic tooth material is solidified into a thirdsolid synthetic tooth material 41. The third fluid synthetic toothmaterial may be solidified by the use of a heater 130, or a light 140,or the third fluid synthetic tooth material may be self-curing, all asdescribed previously with respect to first fluid synthetic toothmaterial 20.

Referring to FIGS. 7-8B, with first, second, and third solid toothmaterials 22, 32, and 42 provided, the finished denture 60 may becompleted. As described previously, the milling bit 102 is traversedover and/or around the block 10, optionally with both the block 10 andthe bit 102 moved relative to each other. Denture base material 13 isremoved from the upper region 15, the lower region 17, and the lateralregion 19 of the block 10, leaving behind the denture base 62.Additionally, first solid synthetic tooth material 21 and third solidsynthetic tooth material 41 are removed by the milling bit 102 asrequired to form the plurality of teeth 64.

In summary, the instant method may be used to produce a denturecomprising a denture base material and synthetic teeth. The syntheticteeth may be comprised of one, two, or three solid synthetic toothmaterials. The synthetic teeth may be made of a single tooth materialwith differing shades and color opacity. Alternatively, the teeth may becomprised of a posterior region of a first solid synthetic toothmaterial and an anterior region of a second solid synthetic toothmaterial. The second solid synthetic tooth material preferably has theappearance to an observer of natural teeth, and may be a translucentmaterial. The teeth may be further comprised of a third solid synthetictooth material in an interior region between the first solid synthetictooth material and the second solid synthetic tooth material. The thirdsolid synthetic tooth material may have the color of natural teeth. Whenused in combination with a second solid tooth material that istranslucent, more natural looking artificial teeth are provided. Incertain embodiments, the solid synthetic tooth materials are polymermaterials. More particularly, in certain embodiments, the solidsynthetic tooth materials may be methyl-methacrylate polymer.

In certain embodiments, the fluid synthetic tooth materials may containsolid particles and/or fibers, such as pigments for coloration, and/orparticles or fibers to improve wear resistance and structural strengthof the artificial teeth. The fluid synthetic tooth materials may beformulated as liquid/solid dispersions. The fluid synthetic toothmaterials may be formulated as hot melt materials that are deliveredinto the cavities in a molten state and then solidify.

The instant method may further comprise heat treating the denture baseand plurality of teeth after their formation. Such heat treatment mayimprove cross-linking of the artificial teeth, thereby improving theirstrength and wear resistance, and it may also improve the chemical bondof the teeth to the denture base. The improved chemical bond is believedto decrease the likelihood of the artificial teeth detaching from thedenture base (referred as a “pop-out”), and the formation of darkdemarcation lines around the junction of the artificial teeth andartificial gingiva due to bacterial growth. (The latter problem is oftenfound in dentures made with porcelain artificial teeth of the currentart, because there is no chemical bond between the denture base and suchporcelain teeth).

The method may further comprise a “touch-up” step, in which any smallimperfections are removed with a small high-speed milling tool. In afinal step, the denture base and teeth may be polished using a polishinglathe to a smooth finish to maximize comfort for the wearer, to minimizebacterial growth on the surfaces, and to maximize aesthetic appearance.

In addition to the instant method, there is also provided an apparatusfor making a denture comprised of a base and a plurality of teeth joinedto the base. In general, the apparatus may include a combination ofcertain hardware operated by a computer that includes certain software.The method and apparatus may be referred to in general as a CAD-CAM(Computer Aided Design/Computer Aided Manufacturing) system. Referringto FIGS. 1A-7, the apparatus may include a material holding fixture (notshown), a material removal device, and a first fluid synthetic toothmaterial delivery device. The material removal device is contactablewith a block of denture base material held by the fixture so as toremove denture base material and form a first mold cavity in the blockfor receiving the first fluid synthetic tooth material. The materialremoval device may be a mill, such as mill 100 comprising mill bit 102of FIG. 1A. The first fluid synthetic tooth material delivery device,such as syringe 120, is configured to deliver the first fluid synthetictooth material 20 into the first mold cavity 12.

The apparatus may be further comprised of a fluid-to-solid toothmaterial curing device configured to cure the first fluid synthetictooth material 20 in the first mold cavity 12 into first solid toothmaterial 21. The fluid-to-solid tooth material curing device may be aheater 130 and/or a light 140, such as an ultraviolet light.

The material holding fixture (not shown) and material removal device 100are movable with respect to each other so as to enable the materialremoval device 100 to remove denture base material 13 from the block 10and first solid tooth material 21 in the first mold cavity 12 so as toform the denture base 62 and at least a portion of the plurality ofteeth 64.

The apparatus may be further comprised of a second fluid synthetic toothmaterial delivery device, such as syringe 220, configured to deliver thesecond fluid synthetic tooth material 30 into a second mold cavity 33formed by the material removal device 100 removing a portion of thefirst solid tooth material 21. In such an embodiment, a fluid-to-solidtooth material curing device such as heater 130 or light 140 may beconfigured to cure the second fluid synthetic tooth material 30 in thesecond mold cavity 33 into second solid tooth material 31. Additionally,the material holding fixture (not shown) and material removal device 100may be movable with respect to each other so as to enable the materialremoval device 100 to remove second solid tooth material 31 in thesecond mold cavity 33 so as to form at least a portion of the pluralityof teeth 64.

The apparatus may be further comprised of a third fluid synthetic toothmaterial delivery device (not shown) configured to deliver the thirdfluid synthetic tooth material into a third mold cavity formed by thematerial removal device 100 removing a portion of the first and/orsecond solid tooth materials 21 and 31. In such an embodiment, afluid-to-solid tooth material curing device such as heater 130 and/orlight 140 may be configured to cure the third fluid synthetic toothmaterial in the third mold cavity into third solid tooth material 41.Additionally, the material holding fixture and material removal device100 may be movable with respect to each other so as to enable thematerial removal device 100 to remove third solid tooth material in thethird mold cavity so as to form at least a portion of the plurality ofteeth 64.

The apparatus may further include a computer for operating the motion ofthe denture base material holding fixture, the material removal device,the fluid synthetic tooth material delivery device(s), thefluid-to-solid tooth material curing device(s), a heat treating device,and final finishing and polishing devices, to the extent such devicesare provided. Accordingly, one or more of the steps of the method may beimplemented by the computer. The computer may be located remotely fromthe remaining components of the apparatus and may be in hardwired orwireless communication with one or more of such components. The computermay include a central processing unit, a memory, a computer-readablestorage medium such as a hard disk, optical disk, or flash memory, and acommunication interface for wireless or hardwired signal communicationwith other components of the apparatus and via the Internet or othercomputer communication network.

The denture to be manufactured may be defined by a digitalthree-dimensional model. The 3D model may be defined by makingmeasurements and/or scanning of the patient's mouth. Alternatively, asdescribed previously, the 3D model may be made by scanning a “try-in”denture that is fitted by a dentist or other clinician to the patient inorder to establish the final dimensions of the denture.

Once the 3D model is completed, it may then be uploaded to and used bythe computer to control the denture-making apparatus and perform thesteps to produce the final denture as described herein. For example,forming a first cavity, delivering first fluid synthetic tooth materialinto the first cavity, solidifying the first synthetic fluid toothmaterial into first solid synthetic tooth material, and removing aportion of the first solid synthetic tooth material to form at least aportion of the plurality of teeth and the removing a portion of theblock of denture base material to form the denture base may be performedby the computer to produce the denture having the dimensions defined inthe three-dimensional model. The computer may perform the processing ofsecond and third solid synthetic tooth materials in a similar manner, ifsuch are made part of the denture.

It is to be understood that while the present disclosure has been setforth as methods and apparatus for making a denture, the methods andapparatus are not limited to only such an article. The instant methodand apparatus are applicable to other dental prostheses such as partialdenture prostheses, occlusal splints, nightguards, orthodonticappliances, crowns, bridges, as well as for the fabrication of othermedical prostheses comprising first and second materials, wherein thefirst material can be used to form a mold for receiving liquid secondmaterial, curing it into solid second material, and then removing aportion of the first and second material to make the medical prosthesisor a portion thereof.

It is, therefore, apparent that there has been provided, in accordancewith the present disclosure, a method and apparatus for themanufacturing of a dental prosthesis, and a denture comprising a baseand a plurality of teeth. Having thus described the basic concept of theinvention, it will be rather apparent to those skilled in the art thatthe foregoing detailed disclosure is intended to be presented by way ofexample only, and is not limiting. Various alterations, improvements,and modifications will occur to those skilled in the art, though notexpressly stated herein. These alterations, improvements, andmodifications are intended to be suggested hereby, and are within thespirit and scope of the invention. Additionally, the recited order ofprocessing elements or sequences, or the use of numbers, letters, orother designations therefore, is not intended to limit the claimedprocesses to any order except as may be specified in the claims.

I claim:
 1. A method of making a denture comprised of a base and aplurality of teeth joined to the base, the method comprising: a) forminga first cavity in a block of a denture base material, the first cavityformed to match the contour of natural teeth as arranged on maxillae oron a mandible; b) filling the first cavity with a first fluid synthetictooth material and solidifying the first fluid synthetic tooth materialinto a first solid synthetic tooth material; c) forming a second cavityby removing a portion of the first solid synthetic tooth material, thesecond cavity formed to match the contour of natural teeth as arrangedfor the contour of the first cavity; d) filling the second cavity with asecond fluid synthetic tooth material and solidifying the second fluidsynthetic tooth material into a second solid synthetic tooth material;e) removing a portion of the second solid synthetic tooth material toform the plurality of teeth; and f) removing a portion of the block ofdenture base material to form the denture base.
 2. The method of claim1, further comprising heat treating the denture base and plurality ofteeth.
 3. The method of claim 1, wherein solidifying the first fluidsynthetic tooth material is performed by heating the first fluidsynthetic tooth material.
 4. The method of claim 1, wherein solidifyingthe first fluid synthetic tooth material is performed by irradiating thefirst fluid synthetic tooth material.
 5. The method of claim 1, whereinsolidifying the first fluid synthetic tooth material is performed byself-curing first fluid synthetic tooth material.
 6. The method of claim1, wherein the denture is defined by a digital three-dimensional model,and wherein the forming the first cavity and the forming the secondcavity are performed based upon data from the three-dimensional model.7. The method of claim 6, wherein the removing a portion of the secondsolid synthetic tooth material to form the plurality of teeth and theremoving a portion of the block of denture base material to form thedenture base are performed to produce the denture having the dimensionsdefined in the three-dimensional model.
 8. The method of claim 7,further comprising making a trial denture, fitting the trial denture toa patient, scanning the fitted trial denture to obtain scanned denturedata, and using the scanned denture data to produce the digitalthree-dimensional model.
 9. The method of claim 1, further comprisingfilling the second cavity with a third fluid synthetic tooth material,solidifying the third fluid synthetic tooth material into a third solidsynthetic tooth material, and removing a portion of the third solidsynthetic tooth material to re-form the second cavity, prior to fillingthe second cavity with the second fluid synthetic tooth material. 10.The method of claim 1, wherein the second solid synthetic tooth materialdiffers from the first solid synthetic tooth material.
 11. The method ofclaim 10, wherein the second solid synthetic tooth material is synthetictranslucent tooth enamel material.
 12. A method of making a denturecomprised of a base and a plurality of teeth joined to the base, themethod comprising: a) forming a first cavity in a block of a denturebase material, the first cavity formed to match the contour of naturalteeth as arranged on maxillae or on a mandible; b) filling the firstcavity with a first fluid synthetic tooth material and solidifying thefirst fluid synthetic tooth material into a first solid synthetic toothmaterial; c) removing a portion of the first solid synthetic toothmaterial to form the plurality of teeth; and d) removing a portion ofthe block of denture base material to form the denture base.
 13. Themethod of claim 12, wherein the first solid synthetic tooth material isa wax.
 14. The method of claim 12, wherein solidifying the first fluidsynthetic tooth material is performed by heating the first fluidsynthetic tooth material.
 15. The method of claim 12, whereinsolidifying the first fluid synthetic tooth material is performed byirradiating the first fluid synthetic tooth material.
 16. The method ofclaim 12, wherein solidifying the first fluid synthetic tooth materialis performed by initiating self-curing of the first fluid synthetictooth material.
 17. The method of claim 12, further comprising heattreating the denture base and/or plurality of teeth.
 18. The method ofclaim 12, wherein the denture is defined by a digital three-dimensionalmodel, and wherein the forming the first cavity is performed based upondata from the three-dimensional model.
 19. The method of claim 12,wherein the denture is defined by a digital three-dimensional model, andwherein the removing a portion of the first solid synthetic toothmaterial to form the plurality of teeth and the removing a portion ofthe block of denture base material to form the denture base areperformed to produce the denture having the dimensions defined in thethree-dimensional model.
 20. An apparatus for making a denture comprisedof a base and a plurality of teeth joined to the base, the apparatuscomprising: a) a material holding fixture; b) a material removal device;and c) a first fluid synthetic tooth material delivery device; whereinthe material removal device is contactable with a block of denture basematerial held by the fixture so as to remove denture base material andform a first mold cavity in the block for receiving first fluidsynthetic tooth material; wherein the first fluid synthetic toothmaterial delivery device is configured to deliver the first fluidsynthetic tooth material into the first mold cavity; and wherein thematerial holding fixture and material removal device are movable withrespect to each other so as to enable the material removal device toremove denture base material from the block and first solid toothmaterial in the first mold cavity so as to form the denture base and atleast a portion of the plurality of teeth.
 21. The apparatus of claim20, further comprising a fluid-to-solid tooth material curing deviceconfigured to cure the first fluid synthetic tooth material in the firstmold cavity into first solid tooth material.
 22. The apparatus of claim20, further comprising a second fluid synthetic tooth material deliverydevice configured to deliver the second fluid synthetic tooth materialinto a second mold cavity formed by the material removal device removinga portion of the first solid tooth material.
 23. The apparatus of claim22, further comprising a fluid-to-solid tooth material curing deviceconfigured to cure the second fluid synthetic tooth material in thesecond mold cavity into second solid tooth material.
 24. The apparatusof claim 23, wherein the material holding fixture and material removaldevice are movable with respect to each other so as to enable thematerial removal device to remove second solid tooth material in thesecond mold cavity so as to form at least a portion of the plurality ofteeth.
 25. The apparatus of claim 24, further comprising a third fluidsynthetic tooth material delivery device configured to deliver the thirdfluid synthetic tooth material into a third mold cavity formed by thematerial removal device removing a portion of at least one of the firstsolid tooth material and the second solid tooth material.
 26. Theapparatus of claim 25, further comprising a fluid-to-solid toothmaterial curing device configured to cure the third fluid synthetictooth material in the third mold cavity into third solid tooth material.27. The apparatus of claim 26, wherein the material holding fixture andmaterial removal device are movable with respect to each other so as toenable the material removal device to remove third solid tooth materialin the third mold cavity so as to form at least a portion of theplurality of teeth.
 28. A denture comprising a base and a plurality ofteeth joined to the base, the teeth comprised of a posterior region of afirst solid synthetic tooth material and an anterior region of a secondsolid synthetic tooth material.
 29. The denture of claim 28, wherein thesecond solid synthetic tooth material has the appearance of naturalteeth to an observer.
 30. The denture of claim 28, wherein the teeth arefurther comprised of a third solid synthetic tooth material in aninterior region between the first solid synthetic tooth material and thesecond solid synthetic tooth material.